This is a really important point - prune on $File::Find::name match works best. e.g.

   my $crnt_file = $File::Find::name;
   my $root = $::root_dir;
   if (scalar grep($crnt_file =~ m/^$root$_/, @::prune) != 0) {
      print Dumper($crnt_file);
      $File::Find::prune = 1;
      return;
    }
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This tip helped heaps. Thanks.